1. Technical Field
The present invention relates to light-emitting elements such as a light-emitting diode (LED).
2. Description of the Related Art
An AlGaInP-based LED has a layered structure in which, e.g., an n-clad layer, an active layer, and a p-clad layer made from AlGaInP are layered on an n-type GaAs substrate; a p-type current-spreading layer made from GaP is formed on the p-clad layer if required; and an electrode is formed on a surface of each of the GaAs substrate and the current-spreading layer. The n-clad layer and the p-clad layer have the composition ratio of Al and Ga adjusted so that the bandgap is greater than that of the active layer, and form a so-called double heterostructure.
Meanwhile, there has been proposed a structure in which, in order to make it possible to increase the brightness of the LED and allow the LED to be driven using a large current, the GaAs substrate used for crystal growth for a semiconductor film is removed, and an Si substrate is bonded onto the semiconductor film interposed by a light-reflecting layer. An Si substrate has a thermal conductivity that is higher than that of a GaAs substrate, which results in an improvement in heat-radiating performance, making it possible for the LED to be driven with a large current.
There are techniques disclosed in, for example, JP-A 2008-053425 (also referred to hereafter as Patent Reference 1) and JP-A 2010-50318 (also referred to hereafter as Patent Reference 2).